Frost Dates for 19609 — Reading, Pennsylvania

Half of springs at Reading Spaatz Field, PA see their last 32°F night by April 14; only one in ten is past it by April 1, and one in ten still has one after April 30. Planting tender crops after April 21 leaves a 30% risk of a frost on them, after April 24 20%, and after April 30 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 51% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 29 in half of years, as early as October 13 one year in ten, and holds off past November 10 one year in ten. A hard freeze of 28°F follows 10 days later, around November 8; in spring the one-in-ten date for 28°F is April 15, 15 days before the 32°F one. The freeze-free season lasts 197 days in a typical year, longer than at 86% of the 176 Pennsylvania stations; it reaches 217 days one year in ten and falls short of 173 one year in ten. On average 107 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 14 days longer, to about April 28, and return around October 17. Severe cold of 16°F or below comes every winter, usually between December 21 and February 28.

July is the warmest month at Reading Spaatz Field, PA, averaging 87°F by day and 66°F at night; January is the coldest at 39°F and 23°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 89% of years.

Warmth for growing adds up to 3,538 growing degree days a year (base 50°F), more than at 90% of the 176 Pennsylvania stations. 35% of them (1,222) have built up by the end of June, and July adds the most, 811. Precipitation totals 45.3 inches a year, most in September (4.9") and least in February (2.6"); May to September bring 50% of it.

The nearest other station, Blue Marsh Lake, PA, 4 miles northwest of Reading, has a last frost 12 days later (April 26), a first frost 10 days earlier (October 19), a season 21 days shorter.

The first measurable snow (0.1 inch or more) in Reading usually arrives around December 8, and the last of the season around March 23. Those are the middle dates across the winters of 1991–2020 at Reading Spaatz Field, PA, 3.2 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 22 days after the last snow.

ZIP 19609 is 3 miles from Reading Spaatz Field, PA, which stands at 341 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 8 other ZIP codes share the station; its figures are presented in full for 19601 (Reading). The 2023 USDA Plant Hardiness Zone Map lists ZIP 19609 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.